Conventionally, a number of electronic wrist watches provided with a calendar function is on the market. These watches include commercial products in which a microcomputer is used to amend a calendar. Initial data, specifically, the month, day, and time at the start of operation of a watch is set by operating a plurality of buttons. Also, the number of days from the start of operation is counted to discriminate which type of month is, specifically, a 31-day month or a month with thirty or less day at the end of the month, thereby amending the displays of the month and day.
In these electronic timepieces, replacement of a battery is inevitable. When a battery is removed for replacement, the time information which has been stored up to that time is cleared. In this case, it has been proposed to adopt a system used in many electric devices in which a secondary power source differing from the primary power source operates to store the time information and the like which must not be lost, the secondary power source is always replenished by a charge from the primary power source, and the secondary power source operates to maintain the memory during replacement of the primary power source. However, it is difficult to incorporate such a system into devices such as electronic timepieces, particularly electronic wrist watches, which are made more convenient by a reduction in size.
In addition, there is the case where watches in the condition that a battery runs out are allowed to stand for over several weeks or several months. Even if the aforementioned system in which the time information is protected using the secondary power source could be realized, such a system would not meet the requirements of this case. There is, among other measures, one in which a non-volatile substance is used to memorize the time information just before a battery runs out and driving hands are suspended. Even such measures are of no use if the period of time during which the watch is allowed to stand is long.
Because of the aforementioned reasons, the above electronic timepieces in which a calendar is corrected using a microcomputer prevail in the market at present.
However, in such an electronic timepiece, as mentioned above, not only a very complicated operation is required to set the initial data when replacing a battery but also the watch must be provided with a number of operating buttons. This causes the decorative shape of the watch to be restricted. Also, since the life of the battery is very long, there is the problem that one may forget how to operate buttons for amending the calendar when the battery is replaced next time.
In view of this situation, it is an object of the present invention to provide an electronic timepiece equipped with a calendar function in which the initial data when a battery is replaced can be set exactly by a simple operation without the necessity for a button attached to the casing of the watch for executing this operation.